The present invention relates to vegetation trimmers. More particularly, the present invention pertains to hand-held, electric string trimmers having a coupling mechanism that permits the trimmer to be configured in either a trimming configuration or an edging configuration.
Hand-held vegetation trimmers are generally known in the art. While these devices may incorporate a variety of cutting elements, perhaps the most popular are string trimmers, i.e., those which utilize a filament line or string as the cutting member.
Although string trimmers are available with a variety of power sources ranging from internal combustion engines to cordless, battery-powered electric motors, it is the plug-in (i.e., corded) variety electric string trimmer that has grown in popularity in recent years. This is primarily attributable to its lightweight construction, ease of operation, and relative low cost.
Electric string trimmers generally include a cutting unit assembly that houses an electric motor. Coupled to the electric motor is a rotatable cutting head having a length of cutting line protruding therefrom. During operation, the cutting head rotates and the cutting line stiffens sufficiently to sever ground-growing vegetation such as grass, weeds, etc.
The cutting unit assembly is typically connected to a handle assembly which incorporates the operator controls and the remote electrical interconnection (e.g., a 120 VAC electrical plug). Preferably, the handle assembly has an ergonomic design which allows the operator to comfortably support and maneuver the trimmer during operation. Lastly, an extension tube assembly is typically provided between the handle assembly and the cutting unit assembly to provide the desired reach therebetween. The handle assembly often includes a secondary handle to accommodate the operator""s second hand. Alternatively, the secondary handle may be attached to the extension tube assembly.
It is advantageous to utilize string trimmers in both a trimming configuration and an edging configuration. In the trimming configuration, the cutting unit assembly is oriented relative to the handle assembly to accommodate comfortable manipulation of the cutting unit for horizontal cutting, e.g., where the axis of the cutting head is vertical. In the edging configuration, the cutting unit assembly is rotated relative to the handle assembly to better accommodate vertical cutting, e.g., where the axis of the cutting head is horizontal.
Trimmers that accommodate this relative motion are known. For instance, some trimmers having cutting unit assemblies that rotate relative to the extension tube. However, these trimmers typically require the operator to grasp or otherwise manually manipulate the cutting unit assembly to change the trimmer configuration. These devices further require the additional step of manually unlocking an index mechanism, e.g., a push-button, lever, or the like, prior to manipulation. While effective, having to grasp or otherwise manually manipulate the cutting unit assembly and unlock the index mechanism is inconvenient.
The present invention provides a vegetation trimmer that is conveniently manipulable between a trimming configuration and an edging configuration. More particularly, the present invention provides a trimmer that may be manipulated between the two configurations by application of a twisting force and optionally a pulling force applied between the handle assembly and the extension tube. Trimmers according the present invention further provide a biasing force that tends to both assist the trimmer towards and retain the trimmer in either the trimming or edging configuration. In embodiments where a secondary handle is provided and tightly coupled to the extension tube, the trimmer may be manipulated between the trimming and edging configurations by simply twisting the secondary handle relative to the handle assembly. In another embodiment, the handle assembly may be longitudinally displaced, relative to the extension tube, prior to or during twisting. The longitudinal displacing force may also be applied between the handle assembly and the secondary handle.
In one embodiment, a vegetation trimmer is provided including a cutting unit assembly and a handle assembly. An extension tube having a first end coupled to the handle assembly and a second end coupled to the cutting unit assembly is also included. A coupling mechanism is also provided. The coupling mechanism is adapted to rotationally bias the handle assembly relative to the cutting unit assembly towards either a first position or a second position wherein the first position corresponds to a trimming configuration and the second position corresponds to an edging configuration.
In another embodiment, a vegetation trimmer is provided wherein the trimmer is adapted for use in either a trimming configuration or an edging configuration. The trimmer includes a cutting unit assembly and a handle assembly. The trimmer further includes an extension tube having a first end coupled to the handle assembly and a second end coupled to the cutting unit assembly, and a coupling mechanism for coupling the first end of the extension tube to the handle assembly. The coupling mechanism includes: a cam member wherein the cam member defines a cam surface; a cam follower for moving along the cam surface; and a biasing member for biasing the cam surface against the cam follower. The coupling mechanism is adapted to allow the handle assembly to be selectively rotated relative to the extension tube by application of a twisting force.
In yet another embodiment, a method for reconfiguring a vegetation trimmer between a trimming configuration and an edging configuration is provided. The method includes providing a vegetation trimmer where the vegetation trimmer has a cutting unit assembly and a handle assembly. The handle assembly is adapted to receive a first hand of an operator. The trimmer further included an extension tube assembly having a first end coupled to the handle assembly and a second end coupled to the cutting unit assembly, wherein the extension tube assembly is adapted to receive a second hand of the operator. A coupling mechanism is also included with the trimmer wherein the coupling mechanism couples the first end of the extension tube assembly to the handle assembly. The coupling mechanism is further adapted to rotationally bias the handle assembly relative to the extension tube assembly to either a first position or a second position, the first position corresponding to the trimming configuration and the second position corresponding to the edging configuration. The method further includes applying a twisting force between the handle assembly and the extension tube assembly whereby the handle assembly rotates about the extension tube assembly between the first position and the second position.